Assessing the usefulness of a novel MRI-based breast density estimation algorithm in a cohort of women at high genetic risk of breast cancer: the UK MARIBS study

Table 5 Breast cancer risk according to MRI absolute dense volume and Cumulus and visual assessment absolute dense areas (Medial-Lateral Oblique view)

	No. women	No. cancers	No. pyears	IRR - binary (95% CI) P-value	IRR - trend (95% CI) P-value
*Adjusted for age ≥ 45 years*
MRI dense volume	651	56	4,291	2.08 (1.20, 3.62) 0.009	1.33 (1.05, 1.70) 0.020
Cumulus MLO dense area	607	42	4,109	0.76 (0.41, 1.41) 0.39	0.96 (0.73, 1.25) 0.75
*Adjusted for age ≥ 45 years, BMI and parity*
MRI dense volume	499	40	3,345	1.87 (0.98, 3.56) 0.058	1.25 (0.94, 1.66) 0.13
Cumulus MLO dense area	456	30	3,123	0.64 (0.30, 1.36) 0.25	0.84 (0.60, 1.19) 0.33
*Adjusted for age ≥ 45 years and BRCA1/2 status/carrier probability*
MRI dense volume	615	53	4,046	2.31 (1.31, 4.07) 0.004	1.42 (1.11, 1.83) 0.006
Cumulus MLO dense area	591	39	4,006	1.19 (0.63, 2.26) 0.59	1.11 (0.82, 1.50) 0.52
*Adjusted for age ≥ 45 years, BRCA1/2 status/carrier probability, BMI and parity*
MRI dense volume	485	39	3,240	2.16 (1.12, 4.17) 0.021	1.35 (1.01, 1.80) 0.042
Cumulus MLO dense area	450	29	3,078	0.99 (0.46, 2.13) 0.99	0.95 (0.64, 1.41) 0.81

BRCA1/2 carrier probabilities estimated using Boadicea for untested women and those with an uninformative test result.
Pyears = number of person-years in study and follow-up period
IRR - trend = incidence rate ratio, estimated assuming a linear trend in risk ratio between quartiles
IRR - binary = incidence rate ratio for the higher two quartiles versus the lower two quartiles
CI = confidence interval.

ISSN: 1465-542X